Incandescent cathode



`lune 18, 1929. I P, vw, DOBBEN ETAL 1,718,123

INCANDESCENT CATHODE Filed July 18, 1927 Panarea June 1s, 1929.

UNITED STATES PATENT OFFICE.

PIETER WILHELM DOBBEN, JOHANNES GIJSBERTUS WILHELM MULDER, .AND EKKO OOSTERHUIS, OF EINDHOVEN, NETHERLANDS, ASSIGNORS TO N. V. PHILIPS GLOEILAMPENFABBIEKEN, F EINDHOVEN, NETHERLANDS, A LIMITED LIABILITY COMPANY 0F THE NETHERLANDS.

INCANDESCENT CATHODE.

Application led July 18, 1927, Serial No. 206,736, and in the Netherlands October 14, 1926.

This invention relates to an improvement in or modification of that described in specilication No.- 171,051 and is concerned with incandescent cathodes, more particularly 5 With those which have a high emitting capacity. According to the prior specification, the incandescent cathode consists of a core of highly refractory and preferably poor heat conducting metal, said core having helically wound on it another metal wire made of a substance of high emitting capacity or superticiallycoated with the said substance.

The applicant has found that the use of nickel for constituting the metal Wire which has to be helically wound on the core of highly refractory metal, offers considerable advantages over the use of other metals. According to the invention, the incandescent cathode according to the prior specification is characterized in that the helically wound metal wire substantially consists of nickel.

As set forth in the prior specification, a metal such as tungsten or molybdenum may be used as material for constituting the core.

The nickel wire wound on this core4 may be coated with an alkaline earth oxide and, if desired, an intermediate layer of another material may be provided.

The invention will be more clearly understood lby referring to -the accompanying drawing representing, by way of example, an embodiment'of the invention.

A stretched core wire 1 made for example of tungsten or molybdenum has helically arranged on it a nickel wire 2. The turns of the latter wire may be adjacent each other as shown in the drawing, but also they may be wound so as to be slightly spaced apart from one another if this should be desirable `for any reason, for example in yview of the steepness of the characteristic of the discharge tube in which the cathode is arranged.

The nickel wire 2 is coated with one or more oxides of the alkaline earths, which may be applied thereto by methods known per se; If desired, a layer of an oxide of another metal, for example copper oxide, may be arranged between the nickel and the alkaline earth oxide. On both sides, the core wire 1 extends outside the ends of the wire 50 helix 2, the ends of the latter being secured to the core wire 1. The protruding ends of the core wire are secured to the leads 3 and 4 which serve to supply the current and which are sealed in a known manner in the pinch of the discharge tube.

What 4We claim is 1. An incandescent cathode for discharge tubes consisting of a core of highly refractory metal, having helically wound on it another metal wire which substantially consists of nickel and is superficially coated with a substance of high emitting capacity.

2. An incandescenty cathode for discharge tubes consisting of a core of highly refractory metal having poor heat conductivity and which core has helically wound on it another metal wire which substantially consists of nickel and is superficially coated with a substance of high emitting capacity.

In testimony whereof we aiix our signatures, at the city of Eindhoven, this 28th day of June 1927.

PIETER WILHELM DOBBEII. JOHANNES GIJSBERTUS WILHELM MULDER. EKKO OOSTERIIUIS. 

